Twinning is a crystal growth anomaly, which has posed a challenge in macromolecular crystallography (MX) since the earliest days. Many approaches have been used to treat twinned data in order to extract structural information. However, in most cases it is usually simpler to rescreen for new crystallization conditions that yield an untwinned crystal form or, if possible, collect data from non-twinned parts of the crystal. Here, we report 11 structures of engineered variants of the E. coli enzyme N-acetyl-neuraminic lyase which, despite twinning and incommensurate modulation, have been successfully indexed, solved and deposited. These structures span a resolution range of 1.45-2.30 Å, which is unusually high for datasets presenting such lattice disorders in MX and therefore these data provide an excellent test set for improving and challenging MX data processing programs.

The datasets (raw difraction images) discussed in this manuscript have been deposited in the publicly available
database zenodo at, https://doi.org/ 10.5281/zenodo.54568 and 10.5281/zenodo.1240503. Structural models and
processed structure factor data deposited in the PDB are available under the accession codes given in Table 1, with
the exception of dataset Y137A, as the R factor indices were not satisfactory for PDB deposition.